General Question

It’s pretty common in Sci-Fi movies to have a spacecraft with rotating arms that create artificial gravity for the craft. Would this really generate sufficient centrifugal force to create artificial gravity? Would those arms need to be moving very fast to achieve 1 G-force (I realize the math would be dependent on the length of the arms)? What about astronauts traveling up and down the length of the arm-shafts themselves, would the artificial gravity get stronger the further away they traveled from the central axis? Would they be constantly vomiting from motion sickness?

Are there other factors that would make this technology impractical or unrealistic, or other interesting consequences of a technology such as this?

9 Answers

? Would those arms need to be moving very fast to achieve 1 G-force (I realize the math would be dependent on the length of the arms)? No.

What about astronauts traveling up and down the length of the arm-shafts themselves, would the artificial gravity get stronger the further away they traveled from the central axis? Yes

Would they be constantly vomiting from motion sickness? If they have training then probably not.

Are there other factors that would make this technology impractical or unrealistic, or other interesting consequences of a technology such as this? Unsure how to answer this one. The impractical aspect is the concept. Astronauts are trained to work in microgravity, and it would cause an unnecessary waste of materials and energy to create a centrifuge. Why bother living in 1 gravity? Living in micro G is a lot more efficient—you can store something anywhere as opposed to on the floor.

@Rarebear “Why bother living in 1g?” If this is a long-term situation (like a hypothetical space habitat) it would prevent bone wasting that occurs when humans live in microgravity for long periods of time.

Centrifugal force = w^2 x r. w is rotational speed (e.g. rpm) and r is distance from the rotational center. It is not hard to increase w and r to get 1g. 1g is good for astronaut bone health, but causes structural difficulties in the structure of the spacecraft. The structural loads vary across the spacecraft. 0g is nice because the mechanical loads are really low. That is good for reducing structural weight, which reduces fuel usage, which reduces weight of fuel, ... Also, it’s a hassle to balance a spacecraft so that the center of gravity is where you actually want it.

It would work better for a space station than for a spacecraft that actually has to go places.
A spacecraft with what amounts to a great big flywheel attached to it will have difficulty maneuvering. Also, better ‘artificial gravity’ (more easily variable, no Coriolis effect) can be obtained just by accelerating.

Long story short is that you really don’t want to go above three RPM unless you want to sicken just about very human inside as the Coriolis effect screws with their inner ears. So we are talking a few hundred meters in diameter here; something easily doable for a space station but not so easy for a mobile thing like a spaceship. Accordingly, most ships in the BattleTech gaming universe get their gravity from acceleration as it avoids most of the issues that @RocketGuy points out.

“In space, it is possible to create “artificial gravity” by spinning your spacecraft or space station. When the station spins, centrifugal force acts to pull the inabitants to the outside. This process could be used to simulate gravity. It wouldn’t be exactly the same, though, because large coriolis forces would also be present, and things would fall in curves instead of straight lines.”

@XOIIO I can think of so many other examples that I can’t pick just that one. And on this stuff, @koanhead knows even more than I do. I will say that if you want an easy-to-read primer on grav decks, Classic BattleTech: Strategic Operations has a nice one. Babylon 5 is another one.